01 · Codes and standards
NFPA 99, Chapter 14 — hyperbaric facilities
Chapter 14 of the Health Care Facilities Code is the document most often cited to a chamber owner and least often read by one. Here is what it actually governs, by subject, with the source for each point.
Scope
What the chapter covers
NFPA 99 establishes criteria for health care services and systems based on risk to patients, staff and visitors, with the stated aim of minimizing fire, explosion and electrical hazards. Its current edition is 2024 (the official NFPA 99 code page).
Chapter 14 sets criteria for the design and operation of hyperbaric chambers and facilities, covering electrical, fire, pressure and gas hazards for chambers used for medical and experimental procedures at gauge pressures from 0 kPa to 690 kPa (0 psi to 100 psi). The chapter’s annex material notes that hyperbaric chambers are found in hospitals, physician offices, private clinics and business occupancies, and that the chapter is intended to provide minimum safeguards regardless of location (UHMS quoting the 2024 edition scope statement).
That last point is the one owners outside hospitals most often miss. NFPA 101 requires occupancies containing hyperbaric facilities to comply with NFPA 99, and its annex states the intent that the requirement apply to hyperbaric facilities in all occupancies — not only health care ones (UHMS quoting NFPA 101 and its annex).
This page cites Chapter 14 by subject, not by paragraph. Numbering for the electrical provisions differs between editions — the same requirements appear under different section numbers in the public code viewer and in the UHMS accreditation manual. Cite requirements by substance and confirm the number against the edition your authority having jurisdiction enforces (public code viewer, UHMS accreditation manual).
Classification
Class A, Class B, Class C
| Class | Definition | Practical meaning |
|---|---|---|
| Class A | Human, multiple occupancy | Multiplace chambers. The most heavily regulated category: fire-rated construction, deluge and handline suppression, in-chamber breathing apparatus per occupant. |
| Class B | Human, single occupancy | Monoplace chambers. Sprinklered room and exclusive-use room still required; the two-hour construction rating and deluge system are not. |
| Class C | Animal, no human occupancy | Built to the ASME Boiler and Pressure Vessel Code rather than PVHO-1. |
NFPA’s own public article confirms the three-class scheme (NFPA Journal). Chapter 14 additionally assigns Category 1 through 4 hyperbaric care classifications based on the consequence of an oxygen or electrical supply failure, and lists which sections apply to existing facilities; a permission-granted reprint of the 2015 edition chapter carries those definitions (the 2015 edition excerpt).
Room and structure
What the code asks of the room
| Fire-resistance rating | A Class A chamber inside a building, plus all ancillary service equipment, must be protected by two-hour fire-resistance-rated construction. This is not required for Class B or Class C chambers. |
|---|---|
| Doors | Connecting doors to the chamber room and to ancillary equipment rooms must be at least B-label, one-and-a-half-hour fire doors. |
| Exclusive use | When used for hyperbaric procedures, the room housing a Class A or Class B chamber must be for the exclusive use of the hyperbaric operation. UHMS emphasises that this means a treatment room, not a storage room, and points facilities to The Joint Commission’s hyperbaric compliance checklist. |
| Foundation | The supporting foundation must be designed to support the chamber, including the added floor stress from any on-site hydrostatic testing — that is, the weight of the test water. No numeric load value is stated in the code. |
| Sprinklers | A hydraulically calculated automatic wet pipe sprinkler system per NFPA 13 is required in the room housing a Class A, B or C chamber and in ancillary equipment rooms; an automatic water mist system per NFPA 750 is permitted as an alternative in the editions reviewed. |
| Gas shutoffs | Shutoff valves for piped gases must be installed where the piping enters the hyperbaric room. |
| Portable extinguisher | NFPA’s summary states the room must contain a 2-A:10B:C portable fire extinguisher. |
| Chamber construction | Chambers must be designed, fabricated, tested and stamped in accordance with ANSI/ASME PVHO-1; viewports and penetrator plates in Class A and Class B chambers are designed and fabricated to PVHO-1. Animal chambers are built to the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1. |
| Interior materials | A Class A chamber floor must be noncombustible; removable deck plates must be mechanically secured and electrically bonded to the hull; interior surfaces are left unfinished or coated with a high-quality epoxy or noncombustible finish. |
Sources for this table: NFPA 99 Chapter 14 via UpCodes, the UHMS accreditation manual and NFPA Journal.
Ventilation and atmosphere
Air supply, temperature, decompression
- Ventilation rate. The minimum ventilation rate for a Class A chamber is 0.085 m³/min (3 ft³/min) of air per occupant not using a breathing-mask overboard dump system, and ventilation must be provided during non-pressurised operation as well as during pressurisation.
- Breathing apparatus. Individual breathing apparatus must be available inside a Class A chamber for each occupant, supplied independently of the chamber atmosphere, designed for simultaneous use by all occupants, and functional at all attainable chamber pressures. In a fire, provision must exist to switch all breathing apparatus to an independent air supply.
- Compressors. Air compressor installations must consist of two or more compressors, sized so the required flow is maintained with any single compressor out of service, and each compressor must be fed from a separate electrical branch circuit. Intakes must be located away from vehicle or engine exhaust and building exhaust outlets. Oil-lubricated compressors are permitted only with air treatment packages designed to produce medical air, including automatic safeguards.
- Temperature. A Class A chamber not used as an operating room must maintain an occupant-comfortable temperature, described in the code as usually 22°C ±2°C (75°F ±5°F). Dehumidification by cold coils is permitted; fan shaft packing must be noncombustible and the lubricant nonflammable.
- Anaesthetics. Flammable inhalation anaesthetics — cyclopropane, ethyl ether, ethylene, ethyl chloride — shall not be used.
- Emergency decompression. The chamber must be capable of decompressing from 3 ATA to surface in less than six minutes for a Class A chamber and less than two minutes for a Class B chamber. NFPA’s own article states the same two limits.
Sources: UpCodes chamber ventilation provisions, UpCodes Chapter 14, UHMS accreditation manual.
Electrical and grounding
The provisions that fail an inspection
| Prohibited in a Class A chamber | Fixed electrical equipment including circuit breakers, line fuses, motor controllers, relays, transformers, ballasts, lighting panels and power panels. |
|---|---|
| Service equipment location | Switchboards, panels and control consoles are located outside the chamber, in its vicinity. |
| Mixed consoles | A console containing both oxygen piping and electrical equipment must be continuously ventilated, or continuously monitored for excessive oxygen concentration whenever the electrical equipment is energised. |
| Power sources | Two independent power sources are required for Class A and Class B chambers. In a hospital, one source is the on-premises emergency generator system; outside a hospital, the emergency system must comply with NFPA 70, Article 700. |
| Critical branch | Life-support-related electrical equipment — in-chamber outlets, emergency lighting, intercom, alarms and fire detectors, fire suppression controls, pressurisation and ventilation controls, and chamber room lighting — must be on the critical branch with power restored within 10 seconds. |
| Fixed wiring | Threaded rigid metal conduit or intermediate metal conduit with waterproof components, made wrench-tight to prevent sparking, with a continuous ground maintained between all conductive surfaces enclosing electrical circuits and the chamber hull. |
| Flexible cords | Type approved for extra-hard utilization per NFPA 70 Table 400.4, including a ground conductor, and meeting NFPA 70 Article 501 requirements. |
| Grounding | All chamber hulls grounded per NFPA 70, Article 250, and the resistance between the grounded chamber hull and the electrical ground shall not exceed 1 ohm. |
| Isolated power | In health care facilities, in-chamber power circuits must be supplied from an ungrounded system with a line isolation monitor per NFPA 70, 517.160. In-chamber branch circuits shall not exceed 125 V or 15 A; portable cord-connected equipment is limited to 120 V and 2 A. |
| Batteries | Sealed and non-offgassing; charging inside the chamber prohibited; limited to 12 V and 48 W. Lithium and lithium-ion batteries are prohibited in the chamber unless accepted or listed for hyperbaric use by the manufacturer or a nationally recognized testing agency. |
| Motors, receptacles, switches | Motors in a Class A chamber must meet NFPA 70, 501.125(a) requirements for the chamber pressure and oxygen concentration, or be totally enclosed. Receptacles and switches must be waterproof, provide a grounding-conductor connection, be supplied from isolated power, and be locking type or labeled against unplugging under load. |
Sources: UpCodes Chapter 14 and the itemised cross-reference list in the UHMS accreditation manual. NFPA 70, the National Electrical Code, is enforced in all fifty states; its current edition is 2026 (the official NFPA 70 code page).
Gases and fire protection
Monitoring, exhaust, suppression
Continuous, with a 23.5 percent alarm
Continuous oxygen monitoring is required in Class A chambers when breathing mixtures greater than 21 percent oxygen by volume are used, and audible and visual alarms must indicate volumetric oxygen concentrations in excess of 23.5 percent.
Compressor air sampled every six months
Air from compressors supplying the chamber atmosphere must be sampled at least every six months, and after any major repair or modification.
Piped outside, screened, signed
Chamber exhaust must be piped outside the building for all classes; each Class B chamber gets an independent exhaust line; exhaust openings are screened with mesh no coarser than 0.12 in.; exhaust lines are signed as oxygen exhaust.
USP grade, CGA C-7 labeling
Treatment gases — breathing air and oxygen — must be USP grade. All gas outlets inside and outside the chamber must be labeled per CGA C-7. Supply piping fed from commercially supplied cylinders requires a particulate filter of 66 microns or finer.
No liquids, no flammable gas storage
Oxygen and other gases shall not be introduced in a liquid state. Flammable gases shall not be used or stored inside the chamber or within the hyperbaric facility, and hazardous materials and flammable gases shall not be stored in the room housing the chamber.
Deluge and handline for Class A
Class A chambers require fire suppression consisting of independently supplied handline-type and deluge-type water systems; portable carbon dioxide extinguishers are not permitted inside the chamber. Class B and C chambers are not required to comply with those provisions. Deluge and handline systems must be functionally tested at least semiannually, and when a Class A suppression system is out of service, appropriate personnel and agencies must be notified and a status sign conspicuously posted.
Sources: UpCodes Chapter 14, UHMS accreditation manual, NFPA Journal.
Administration and maintenance
Which provisions carry a number
This is the part that matters most to a service contractor, and the part most often misrepresented. Chapter 14 requires that a routine maintenance program exist and be documented. For the chamber and its valves, it does not name an interval.
| Provision | Requirement | Interval in the code |
|---|---|---|
| Valves, regulators, meters | The safety director ensures they are proper, safe and compensated for hyperbaric use, and tested per the facility’s routine maintenance program. | None stated |
| Pressure relief valves | Tested and calibrated as part of the routine maintenance program. | None stated |
| Replacement parts | All replacement parts and components conform to the original design specification. | — |
| Installation, repair, modification | Must receive an engineering evaluation, be tested under pressure, and be approved in writing by the safety director. | — |
| Maintenance log | The safety director maintains a log of all maintenance and tests on chamber equipment and systems; operating equipment logs are signed by the safety director before the chamber returns to service. | — |
| Electrical, monitoring, life support, ventilating arrangements | Inspected and tested per the routine maintenance program. | None stated |
| Chamber electrical circuits | Tested per the routine maintenance program, including a ground-fault check confirming no conductors are grounded to the chamber, plus a test of normal functioning. | None stated |
| Fire detection and extinguishment controls | Electrical switches, valves and monitoring equipment visually inspected. | Before each pressurization |
| Fire detection equipment | Trouble circuits and signals tested; full testing including discharge of extinguishing media. | Weekly / annually |
| Rubber-containing materials | Inspected for cracking and degradation. | “Regularly” |
| Conductive path integrity | Furniture leg tips, tires and casters inspected free of wax or lint that would insulate them; no impact-sparking metals; casters lubricated only with flame-resistant, oxygen-compatible lubricants. | — |
| Housekeeping | A regular housekeeping program keeping the facility free of grease, lint, dirt and dust, with staff training documented. | — |
| Emergency procedures and fire drills | Hyperbaric-specific drills practiced by all hyperbaric personnel and documented; evacuation time measured during the drill. | Annually |
Chapter 14 does not codify a monthly, quarterly or annual preventive-maintenance interval for the chamber itself and its valves. It requires that a routine maintenance program exist, that it cover these items, and that testing be logged and signed off. The cadence comes from the manufacturer’s manual, your own documented program, ASME PVHO-2 for windows and gauges, and voluntary programs such as UHMS accreditation. Anyone who quotes you a code-mandated annual chamber PM interval should be asked which paragraph they mean.
Sources for the table: UpCodes Chapter 14 and the itemised cross-reference list in the UHMS accreditation manual.
Operations
Safety director and prohibitions
Chapter 14 requires that a hyperbaric safety director be designated in writing and be in charge of all hyperbaric equipment and the operational safety requirements of the chapter; UHMS quotes the code requiring the medical director of hyperbaric medicine and the safety director to jointly develop minimum staff qualifications and experience (NFPA 99 first-draft committee material, UHMS accreditation and licensure FAQ).
Prohibited in the chamber and its immediate vicinity: smoking, open flames and hot objects. Prohibited inside the chamber: personal warming devices, cell phones and pagers, sparking toys and personal entertainment devices. Flammable liquids, gases and vapours are not permitted inside any Class B chamber. Equipment made of cerium, magnesium or magnesium alloys is prohibited from the chamber interior; in-chamber equipment requiring lubrication uses oxygen-compatible, flame-resistant lubricant; oxygen containers, valves and fittings should be metal as far as possible, with seats, gaskets, hoses and lubricants selected for oxygen compatibility. Paper taken into a Class A chamber must be stored in a closed metal container, emptied after each operation (UpCodes Chapter 14, UHMS accreditation manual).
Hyperbaric Service Pros installs, services, and maintains hyperbaric equipment. We are not a medical facility and do not provide medical advice or treatment. Technical information on this site is general reference only — always follow your chamber manufacturer's documentation and the codes enforced in your jurisdiction.
Sources
Every claim on this page, traced to its source
- NFPA 99, Health Care Facilities Code — official code page (current edition 2024)https://www.nfpa.org/codes-and-standards/nfpa-99-standard-development/99
- NFPA 70, National Electrical Code — official code page (current edition 2026)https://www.nfpa.org/codes-and-standards/nfpa-70-standard-development/70
- NFPA free read-only access to codes and standardshttps://www.nfpa.org/for-professionals/codes-and-standards/list-of-codes-and-standards/free-access
- NFPA 99 Chapter 14, Hyperbaric Facilities — UpCodes public viewerhttps://up.codes/viewer/centers-for-medicare-and-medicaid-services/nfpa-99-2012/chapter/14/hyperbaric-facilities
- NFPA 99 Chapter 14, chamber ventilation provisions — UpCodeshttps://up.codes/s/chamber-ventilation
- NFPA Journal, “Under Pressure,” Brian O’Connor, Aug. 23, 2021https://www.nfpa.org/news-blogs-and-articles/nfpa-journal/2021/08/23/nfpa-13-august
- NFPA 99 hyperbaric technical committee first-draft agenda (A2023)https://docinfofiles.nfpa.org/files/AboutTheCodes/99/99_A2023_HEA_HYP_FD_Agenda_7_21.pdf
- NFPA 99-2015 Chapter 14 partial reprint (permission-granted excerpt)https://www.nbsteampages.com/_fileassets/forms/2015_NFPA_99_Ch14.pdf
- UHMS Clinical Hyperbaric Facility Accreditation Manual, 4th ed.https://www.uhms.org/images/Accreditation-Documents/Fourth_Edition_UHMS_Accreditation_Manual_Final.pdf
- UHMS, “Consumer Warning: The Dangers of Soft-Sided Bag Chambers”https://uhms.org/pressure-other-articles/1542-consumer-warning.html
- UHMS Safety Committee FAQ — standards and codeshttps://www.uhms.org/tl/resources/featured-resources/medfaqs-frequently-asked-questions-faq/safety-technical/standards-and-codes.html
- UHMS Safety Committee FAQ — accreditation and licensurehttps://www.uhms.org/el/resources/featured-resources/medfaqs-frequently-asked-questions-faq/safety-technical/accreditation-and-licensure.html
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